JP2001235677A - Objective lens and DVD / CD compatible optical pickup device - Google Patents

Abstract

(57) [Problem] To provide a DVD / CD compatible optical pickup device which has more stable optical characteristics even with environmental changes, has less loss of light amount, can be obtained in a small size, light weight and inexpensive. Provided is an extremely practical objective lens as an objective lens, and a DVD / CD compatible optical pickup device using the objective lens. An objective lens for a DVD / CD compatible optical pickup device and a DVD / CD compatible optical pickup device having excellent optical characteristics capable of suppressing whitening or the like against environmental changes by using a cyclic olefin resin. Can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an objective lens suitable as an objective lens for a DVD / CD compatible optical pickup device and a DVD / CD compatible optical pickup device using the same.

[0002]

2. Description of the Related Art In recent years, with the practical use of short-wavelength red semiconductor lasers, the development of conventional optical disks, ie, CDs (compact disks) and DVDs (digital video disks), which are optical information recording media, has been progressing. In the optical system of the optical information recording / reproducing apparatus using such an optical disk or the like as a medium, it is preferable to use a glass lens from the viewpoint of stability of optical characteristics with respect to environmental changes.

[0003]

However, the glass lens has a problem that it takes much time to manufacture. On the other hand, since resin lenses can be molded using a mold, mass production of products having a certain quality is possible. However, the resin lens has a problem that the stability of the optical characteristics with respect to environmental changes is inferior to the glass lens.
For example, acrylic, which is one of the resins, is relatively excellent in transparency, but has a problem that the refractive index changes due to moisture absorption. In recent years, in DVDs and the like that have been developed, in order to further increase the information recording density, it is required to further reduce the spot diameter of the information recording light. In such a case, the refractive index of the objective lens is increased. If it changes, there is a possibility that the focus position shifts, thereby causing an information recording / reproducing error. Therefore, an objective lens for an optical pickup device having more stabilized optical characteristics is desired.

[0004] In addition, recording and / or recording of a DVD with a high density is performed.
In addition, it is unreasonable that recording and / or reproduction of a relatively low-density CD cannot be performed in a device such as an audio / video recording / reproducing player equipped with an optical pickup device capable of reproducing, and one optical pickup device is also used. And DVD / C
There is a strong demand for an optical pickup device capable of recording and / or reproducing D together. And such DVD / C
As an objective lens suitable for a D-compatible optical pickup device, it is inevitable to pursue further miniaturization (small diameter and thinner), lighter weight, and lower cost.

SUMMARY OF THE INVENTION The present invention provides an objective lens for a DVD / CD compatible optical pickup device, which has more stable optical characteristics with respect to environmental changes, has less loss of light amount, can be obtained in a small size, light weight and inexpensive. It is an object of the present invention to provide a highly practical objective lens and a DVD / CD compatible optical pickup device using the objective lens.

[0006]

According to the present invention, there is provided an objective lens for a DVD / CD compatible optical pickup device, wherein the objective lens has a diffraction surface and uses a composition containing an olefin resin. It is characterized by being formed.

[0007] Unlike acryl and the like, olefin resins hardly change refractive index due to moisture absorption.
The desired optical performance of a sophisticated objective lens having a diffractive surface for a / CD compatible optical pickup device is hardly degraded, and DVD / CD compatible performance can be easily secured. In addition, since the olefin resin has a higher refractive index than acrylic, it can be designed with a relatively thick end thickness of the objective lens, thereby improving the moldability and transferability of the objective lens. Thus, an objective lens having a high-viscosity diffraction surface and excellent DVD / CD compatibility can be obtained.

[0008] The objective lens according to claim 2 is a DVD /
An objective lens used for a CD compatible optical pickup device, having a diffractive surface and having a melt flow rate MFR of 3
It is characterized by being formed using a composition satisfying 0 to 60 (g / 10 minutes).

The melt flow rate MFR is described in J.
It is defined in ISK7210. When the melt flow rate MFR is from 30 to 60, the birefringence is reduced, and the transferability to a mold during molding is improved.
An objective lens having a D-compatible optical performance and a highly accurate diffraction surface can be obtained.

[0010] The objective lens according to claim 3 is a DVD /
An objective lens used in a CD compatible optical pickup device has a diffractive surface, is exposed to an ambient temperature of 80 ° C. and a humidity of 90% for 48 hours, and then left indoors for 3 hours.
When a light beam having a wavelength of 0 nm and an outer diameter of 1 mm is irradiated, the transmittance is reduced by 6% or less.

One problem with olefin resins is that
This means that whitening is likely to occur. Since the olefin-based resin has no hygroscopic action, water molecules are interposed between the molecules, and when this is vaporized, fine cracks are generated in the material, which is considered to be recognized as whitening. When whitening occurs in the objective lens, the transmittance of the objective lens decreases, so that it is not possible to secure a sufficient intensity of information recording light on the optical disk, and the reading accuracy of information decreases. By satisfying that the above transmittance decrease is 6% or less, it becomes possible to maintain the light quantity and accuracy required for a high-density DVD even under various environments. still,
The decrease in transmittance is preferably 4% or less, and more preferably 2% or less.

According to a fourth aspect of the present invention, the objective lens is formed by using a composition containing an olefin resin.

The objective lens described in claim 5 is characterized in that the objective lens is formed using a composition satisfying a melt flow rate MFR of 30 to 60 (g / 10 minutes).

[0014] The objective lens according to claim 6 is characterized in that the composition contains an olefin resin.

According to a seventh aspect of the present invention, the olefin resin is a cyclic olefin resin [A]. [A] is excellent in reducing birefringence and improving transferability, and can obtain an objective lens that can be miniaturized and has a precise diffraction surface as an objective lens for a DVD / CD compatible optical pickup device. In particular, [A-
1] [A-2] and [A-3] are preferred.

In the present invention, as the cyclic olefin resin, a random copolymer of [A-1] ethylene and a cyclic olefin represented by the following formula [1] or [2], [A-2] A ring-opening polymer or copolymer of a cyclic olefin represented by the following formula [Chemical Formula 1] or [Chemical Formula 2], or [A-3] the ring-opening polymer or copolymer [A-
2] is used. Hereinafter, the cyclic olefin represented by the formula [formula 1] or [formula 2] that forms such cyclic olefin-based resins [A-1] to [A-3] will be described. Cyclic olefin

[0017]

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In the above formula [Formula 1], n is 0 or 1, m is 0 or a positive integer, and q is 0 or 1. When q is 1, R ^a and R ^b are each independently the following atoms or hydrocarbon groups. When q is 0, each bond is bonded to form a 5-membered ring. Form.

R ^{1 to} R ¹⁸ and R ^a and R ^b are each independently a hydrogen atom, a halogen atom or a hydrocarbon group. Here, the halogen atom is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

The hydrocarbon groups each independently include an alkyl group usually having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, and an aromatic hydrocarbon group. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an amyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, and an octadecyl group. A cyclohexyl group is mentioned, and a phenyl group, a naphthyl group, etc. are mentioned as an aromatic hydrocarbon group.
These hydrocarbon groups may be substituted with a halogen atom.

Further, in the above formula [formula 1], R ^15-
R ¹⁸ may be bonded to each other (together with each other) to form a monocyclic or polycyclic ring, and the monocyclic or polycyclic ring thus formed may have a double bond. .
Specific examples of the monocyclic or polycyclic rings formed here are shown below.

[0022]

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In the above examples, the carbon atoms numbered 1 or 2 are the carbon atoms to which R ¹⁵ (R ¹⁶ ) or R ¹⁷ (R ¹⁸ ) are bonded in the formula [Formula 1], respectively. Is shown. R ¹⁵ and R ¹⁶ , or R ¹⁷ and R ^{16
And 18} may form an alkylidene group. Such an alkylidene group is usually an alkylidene group having 2 to 20 carbon atoms, and specific examples of such an alkylidene group include an ethylidene group, a propylidene group and an isopropylidene group.

[0024]

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In the above formula [Formula 2], p and q are 0 or a positive integer, and m and n are 0, 1 or 2. R ^{1 to} R ¹⁹ are each independently a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group.

The halogen atom has the same meaning as the halogen atom in the above formula [formula 1]. Examples of the hydrocarbon group each independently include an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, and an aromatic hydrocarbon group. Can be More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an amyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, and an octadecyl group. A cyclohexyl group; examples of the aromatic hydrocarbon group include an aryl group and an aralkyl group;
Specific examples include a phenyl group, a tolyl group, a naphthyl group, a benzyl group and a phenylethyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. These hydrocarbon groups and alkoxy groups may be substituted with a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

Where R⁹And R^TenCharcoal to which is bound
An element atom and R¹³Is bonded to a carbon atom or R¹¹Tied
The carbon atoms that are combined are directly or having 1 to 1 carbon atoms.
And 3 may be bonded via an alkylene group. Sand
The two carbon atoms are linked via an alkylene group
If there is⁹And R¹³A group represented by or
R^TenAnd R¹¹The groups represented by
Group (-CH_Two-), Ethylene group (-CH_TwoCH_Two−)
Or a propylene group (-CH_TwoCH_TwoCH_Two−)
Some alkylene groups are formed. Further, n = m
When = 0, R ^FifteenAnd R¹²Or R^FifteenAnd R¹⁹Is connected to each other
May combine to form a monocyclic or polycyclic aromatic ring.
No. In this case, as a monocyclic or polycyclic aromatic ring,
For example, when n = m = 0 as shown below, R^FifteenAnd R¹²But also
A group forming an aromatic ring is exemplified.

[0028]

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Here, q has the same meaning as q in the formula [Formula 2]. The cyclic olefin represented by the above-mentioned formula [formula 1] or [formula 2] is more specifically exemplified below.

[0030]

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(In the above formula, the numbers 1 to 7 indicate the position numbers of carbon.) And this bicyclo [2.2.1] -2
-A derivative in which heptene is substituted by a hydrocarbon group. Examples of this hydrocarbon group include 5-methyl, 5,6-dimethyl, 1-methyl, 5-ethyl, 5-n-butyl,
Isobutyl, 7-methyl, 5-phenyl, 5-methyl-
5-phenyl, 5-benzyl, 5-tolyl, 5- (ethylphenyl), 5- (isopropylphenyl), 5-
(Biphenyl), 5- (β-naphthyl), 5- (α-naphthyl), 5- (anthracenyl), 5,6-diphenyl and the like.

Still other derivatives include cyclopentadiene-acenaphthylene adduct, 1,4-methano-1,
Bicyclo [2.2.1] -2-heptene derivatives such as 4,4a, 9a-tetrahydrofluorene and 1,4-methano-1,4,4a, 5,10,10a-hexahydroanthracene.

Tricyclo [4.3.0.1 ^2,5 ] -3-
Decene, 2-methyltricyclo [4.3.0.1 ^2,5 ]
-3-decene, 5-methyltricyclo [4.3.0.1
Tricyclo [4.3.0.1 such as ^2,5 ] -3-decene
^2,5 ] -3-decene derivative, tricyclo [4.4.0.
1 ^2,5] -3-undecene, 10-methyltricyclo [4.4.0.1 ^2,5] -3-tricyclo undecene [4.4.0.1 ^2,5] -3-undecene Derivatives.

[0034]

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(In the above formula, the numbers 1 to 12 indicate the position numbers of carbon atoms.) And derivatives obtained by substituting them with hydrocarbon groups. Examples of the hydrocarbon group include 8-methyl, 8-ethyl, 8-propyl, 8-butyl, 8-isobutyl, 8-hexyl, 8-cyclohexyl, 8-stearyl, 5,10-dimethyl, 2,10 -Dimethyl,
8,9-dimethyl, 8-ethyl-9-methyl, 11,1
2-dimethyl, 2,7,9-trimethyl, 2,7-dimethyl-9-ethyl, 9-isobutyl-2,7-dimethyl, 9,11,12-trimethyl, 9-ethyl-11,
12-dimethyl, 9-isobutyl-11,12-dimethyl, 5,8,9,10-tetramethyl, 8-ethylidene, 8-ethylidene-9-methyl, 8-ethylidene-9
-Ethyl, 8-ethylidene-9-isopropyl, 8-ethylidene-9-butyl, 8-n-propylidene, 8-n
-Propylidene-9-methyl, 8-n-propylidene-
9-ethyl, 8-n-propylidene-9-isopropyl, 8-n-propylidene-9-butyl, 8-isopropylidene, 8-isopropylidene-9-methyl, 8-isopropylidene-9-ethyl, 8-isopropylidene Reden
9-isopropyl, 8-isopropylidene-9-butyl, 8-chloro, 8-bromo, 8-fluoro, 8,9-
Dichloro, 8-phenyl, 8-methyl-8-phenyl,
8-benzyl, 8-tolyl, 8- (ethylphenyl),
8- (isopropylphenyl), 8,9-diphenyl,
8- (biphenyl), 8- (β-naphthyl), 8- (α
-Naphthyl), 8- (anthracenyl), 5,6-diphenyl and the like.

Still other derivatives include adducts of (cyclopentadiene-acenaphthylene adduct) with cyclopentadiene. Pentacyclo [6.5.
1.1 ^3,6 . 0 ^2,7 . 0 ^9,13 ] -4-pentadecene and derivatives thereof. Pentacyclo [7.4.0.1 ^2,5 . 1
^9,12 . 0 ^8,13 ] -3-pentadecene and derivatives thereof. Pentacyclo [6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13
] Pentacyclopentadecadiene compounds such as -4,10-pentadecadiene. Pentacyclo [8.4.0.
^12.5 . ^19,12 . 0 ^8,13 ] -3-hexadecene, and derivatives thereof. Pentacyclo [6.6.1.1 ^3,6 .
0 ^2,7 . 0 ^9,14 ] -4-hexadecene and derivatives thereof. Hexacyclo [6.6.1.1 ^3,6 . 1 ^10,13 . 0
^2,7 . 0 ^9,14] -4-heptadecene and derivatives thereof. Heptacyclo [8.7.0.1 ^2,9 . 1 to ^4, 7. 1
^11,17 . 0 ^3,8 . 0 ^12,16 ] -5-eicosene and derivatives thereof. Heptacyclo [8.8.0.1 ^2,9 . ^14,7 .
1 ^11,18 . 0 ^3,8 . 0 ^12,17 ] -5- ^heneicosene and derivatives thereof. Octacyclo [8.8.0.1 ^2,9 .
^14,7 . ^{11 , 18} . 1 ^13,16 . 0 ^3,8 . 0 ^12,17 ] -5-docosene and derivatives thereof. Nonacyclo [10.9.
1.1 ^4,7 . 1 ^13,20 . 1 ^15,18 . 0 ^2,10 . 0 ^3,8 . 0
^12,21 . 0 ^{1 4, 19]} -5-pentacosene and derivatives thereof. Nonacyclo [10.10.1.1 ^5,8 . 1 ^14,21 . 1
^16,19 . 0 ^2,11 . 0 ^4,9 . 0 ^13,22 . 0 ^15,20] -6-hexacosenoic, and the like derivatives thereof.

The specific examples of the cyclic olefin represented by the general formula [Formula 1] or [Formula 2] are shown above.
Paragraph Nos. [0032] to 196475 of the original specification
Examples of the structure of the cyclic olefin shown in [0054] can be given. The lens composition of the present invention may contain two or more units derived from the above-mentioned cyclic olefin.

The cyclic olefin represented by the above-mentioned general formula [formula 1] or [formula 2] is produced by subjecting cyclopentadiene and an olefin having a corresponding structure to a Diels-Alder reaction. Can be.

The cyclic olefin resin used in the present invention can be prepared by using a cyclic olefin represented by the above-mentioned formula [1] or [2], for example, as disclosed in JP-A-60-1.
No. 68708, No. 61-120816, No. 61-11
No. 5912, No. 61-115916, No. 61-271
No. 308, No. 61-272216, No. 62-2524
It can be produced by appropriately selecting the conditions in accordance with the methods proposed in JP-A Nos. 06 and 62-252407.

[A-1] Random copolymer of ethylene and cyclic olefin [A-1] In the random copolymer of ethylene and cyclic olefin, the unit derived from ethylene is usually 5 to 95 mol%, preferably 20 to 95 mol%. In an amount of 80 mol%,
The unit derived from a cyclic olefin is usually contained in an amount of 5 to 95 mol%, preferably 20 to 80 mol%.
The ethylene composition and the cyclic olefin composition are 13C
-It can be measured by NMR.

In the [A-1] ethylene / cyclic olefin random copolymer, the units derived from ethylene and the units derived from the cyclic olefin are randomly arranged and bonded to form a substantially linear unit. It has a like structure. The fact that the copolymer is substantially linear and does not have a substantially gel-like cross-linked structure means that when the copolymer is dissolved in an organic solvent, the solution contains an insoluble component. You can confirm by not having. For example, when the intrinsic viscosity [η] is measured, it can be confirmed by completely dissolving this copolymer in decalin at 135 ° C.

[A-1] Ethylene used in the present invention
In the cyclic olefin random copolymer, at least a part of the cyclic olefin represented by the above formula [Formula 1] or [Formula 2] is a repeating unit represented by the following formula [Formula 3] or [Formula 4]. It is considered to constitute.

[0043]

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In the formula [Formula 3], n, m, q, R1
To R18 and R ^a and R ^b have the same meanings as in the formula [Formula 1].

[0045]

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In the formula [Formula 4], n, m, p, q and R ^{1 to} R ¹⁹ have the same meaning as in the formula [Formula 2]. Further, the [A-1] ethylene / cyclic olefin random copolymer as described above has a unit derived from another copolymerizable monomer as needed as long as the object of the present invention is not impaired. More specifically, the unit derived from another monomer is usually 20 mol% or less, preferably 10 mol% or less.
It may be contained in an amount of at most mol%.

Examples of such other monomers include olefins other than the above-mentioned ethylene or cyclic olefin, and specific examples thereof include propylene, 1-butene, 1-pentene, 1-hexene, and 3-olefin. Methyl-1-
Butene, 3-methyl-1-pentene, 3-ethyl-1-
Pentene, 4-methyl-1-pentene, 4-methyl-1
-Hexene, 4,4-dimethyl-1-hexene, 4,4
-Dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene Α-olefins having 3 to 20 carbon atoms such as cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene and cyclooctene;
3a, 5,6,7a-tetrahydro-4,7-methano-
Cycloolefins such as 1H-indene, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene,
Non-conjugated dienes such as dicyclopentadiene and 5-vinyl-2-norbornene can be mentioned. The ethylene / cyclic olefin random copolymer [A-1]
It may contain two or more units derived from the above other monomers.

The ethylene / cyclic olefin random copolymer [A-1] is prepared by using ethylene and a cyclic olefin represented by the formula [1] or [2] by the production method disclosed in the above publication. Can be manufactured. Among them, a copolymerization reaction is carried out in a hydrocarbon solvent, and a random copolymer of ethylene / cyclic olefin [A- is used, using a catalyst formed from a vanadium compound and an organoaluminum compound soluble in the hydrocarbon solvent as a catalyst.
1] is preferably manufactured.

Further, using a solid group IV metallocene catalyst, an ethylene / cyclic olefin random copolymer [A-
1] can also be manufactured. This solid group IV metallocene catalyst comprises a transition metal compound (metallocene compound) containing at least one ligand having a cyclopentadienyl skeleton, an organic aluminum oxy compound, and, if necessary, an organic aluminum compound. It is formed. Here, the group IV transition metal is zirconium, titanium or hafnium. Examples of the ligand having a cyclopentadienyl skeleton include a cyclopentadienyl group, an indenyl group, a tetrahydroindenyl group, and a fluorenyl group which may be substituted with an alkyl group. These groups may be bonded via another group such as an alkylene group. Ligand other than the ligand containing a cyclopentadienyl skeleton is usually an alkyl group, a cycloalkyl group, an aryl group,
Aralkyl groups and the like.

As the organic aluminum oxy compound and the organic aluminum compound, those usually used for producing an olefin polymer can be used. Such solid group IVB metallocene catalysts are described in detail in, for example, JP-A-61-221206, JP-A-64-106, and JP-A-2-173112.

[A-2] Ring-opening (co) polymer of cyclic olefin In the ring-opening polymer or ring-opening copolymer of cyclic olefin [A-2], the above formula [1] or [2] It is considered that at least a part of the unit derived from the cyclic olefin represented by the formula [1] is represented by the following formula [5] or [6].

[0052]

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In the formula [Formula 5], n, m, q and R ^{1 to} R ¹⁸ and R ^a and R ^b have the same meaning as in the formula [Formula 1].

[0054]

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In the formula [6], n, m, p, q and R ^{1 to} R ¹⁹ have the same meaning as in the formula [2]. Such a ring-opened (co) polymer can be produced by the production method disclosed in the above-mentioned gazette. For example, a cyclic olefin represented by the above-mentioned formula [formula 1] can be produced in the presence of a ring-opening polymerization catalyst. It can be produced by polymerization or copolymerization.

Examples of such a ring-opening polymerization catalyst include a catalyst comprising a halide, nitrate or acetylacetone compound of a metal selected from ruthenium, rhodium, palladium, osmium, indium or platinum, and a reducing agent; A catalyst comprising a halide or acetylacetone compound of a metal selected from palladium, zirconium or molybdenum and an organoaluminum compound can be used.

[A-3] A hydride of a ring-opening (co) polymer A hydride of a ring-opening (co) polymer [A-3] is a ring-opening polymer or a ring-opening copolymer as described above. A-2] in the presence of a conventionally known hydrogenation catalyst.

The hydride of this ring-opened (co) polymer [A-
In [3], it is considered that at least a part of the unit derived from the formula [Formula 1] or [Formula 2] is represented by the following formula [Formula 7] or [Formula 8].

[0059]

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In the formula [Formula 7], n, m, q and R ^{1 to} R ¹⁸ and R ^a and R ^b have the same meaning as in the formula [Formula 1].

[0061]

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In the formula [Formula 8], n, m, p, q,
R ^{1 to} R ¹⁹ have the same meaning as in the formula [Formula 2]. In the present invention, as the cyclic olefin resin [A], any one of the above [A-1], [A-2] and [A-3] may be used alone, and two or more of the same may be used. These may be used, or they may be used in combination.

Among these, as the cyclic olefin resin [A], an ethylene / cyclic olefin random copolymer [A-1] is preferably used. The crystallinity of the cyclic olefin resin measured by the X-ray diffraction method is 0.
-20%, preferably 0-2%. The softening point temperature (TMA) of the cyclic olefin resin [A] used in the present invention is 80 ° C. or higher, preferably 90 ° C.
To 250 ° C, more preferably 100 to 200 ° C. The glass transition temperature (Tg) is desirably 60 to 230 ° C, preferably 70 to 210 ° C. [A] The limiting viscosity [η] (in decalin at 135 ° C.) of the cyclic olefin resin is 0.05 to 10 dl / g, preferably 0.08 to 5 dl / g.

That is, in the objective lens according to the sixth aspect, the olefin resin may have the following [A-1] to [A-
3] is characterized by having at least one repeating unit selected from the group consisting of: [A-1] a random copolymer of ethylene and a cyclic olefin represented by the above chemical formula [Formula 1] or [Formula 2]; (In the chemical formula [Formula 1], n is 0 or 1, and m
Is 0 or a positive integer; q is 0 or 1;
^{1 to} R ¹⁸ and R ^a and R ^b are each independently a hydrogen atom, a halogen atom or a hydrocarbon group optionally substituted with halogen, and R ^{15 to} R ¹⁸ are bonded to each other to form a monocyclic or polycyclic ring. And the monocyclic or polycyclic ring may have a double bond, and may form an alkylidene group with R ¹⁵ and R ¹⁶ or with R ¹⁷ and R ^18. You may. (In the chemical formula [Formula 2], p and q are 0 or a positive integer, m and n are 0, 1 or 2, and R ^{1 to} R ¹⁹ are each independently a hydrogen atom, a halogen atom, a halogen atom, And a carbon atom to which R ⁹ or R ¹⁰ is bonded, a carbon atom to which R ¹³ is bonded, or a carbon atom to which R ¹¹ is bonded. May be bonded directly or via an alkylene group having 1 to 3 carbon atoms, and n = m =
When 0, R ¹⁵ and R ¹² or R ¹⁵ and R ¹⁹ may combine with each other to form a monocyclic or polycyclic aromatic ring. [A-2] a ring-opened polymer or copolymer of the cyclic olefin represented by the chemical formula [Chemical Formula 1] or [Chemical Formula 2], and [A-3] a ring-opened polymer or copolymer [A-3] A-2]
Hydride.

The objective lens according to the ninth aspect is characterized in that the composition contains a compound having a hydrophilic group and a hydrophobic group in the same molecule.

The lens composition of the present invention contains a compound [B] having a hydrophilic group and a hydrophobic group in the same molecule (hereinafter also referred to as component [B]). The lens composition of the present invention particularly includes the compound [B] having a hydrophilic group and a hydrophobic group in the same molecule as described above,
Even when the environment changes from a high-temperature and high-humidity atmosphere to a normal-temperature and normal-humidity atmosphere, the whitening can be further suppressed, the decrease in transmittance can be reduced, and excellent transparency can be maintained.

Specific examples of the above hydrophilic group include a hydroxy group, a hydroxyalkyl group having 1 or more carbon atoms, a hydroxyl group, a carbonyl group, an ester group, an amino group,
Amide group, ammonium salt, thiol, sulfonate,
Phosphates, polyalkylene glycol groups and the like can be mentioned, and the amino group may be primary, secondary, or tertiary. Specific examples of the hydrophobic group include an alkyl group having 6 or more carbon atoms which may have an aromatic group, a silyl group having an alkyl group having 6 or more carbon atoms, and a fluoroalkyl group having 6 or more carbon atoms. . Specific examples of the alkyl group include hexyl, heptyl, octyl, nonyl, decyl, undecenyl, dodecyl, tridecyl, tetradecyl, myristyl, stearyl, lauryl, palmityl, cyclohexyl, and the like. Examples of the aromatic group include a phenyl group. This component [B] may have at least one hydrophilic group and one hydrophobic group as described above in the same molecule, and may have two or more of each group.

As the compound [B] having a hydrophilic group and a hydrophobic group in the same molecule, more specifically, for example, myristyldiethanolamine, 2-hydroxyethyl-2-hydroxydodecylamine, 2-hydroxyethyl -2-hydroxytridecylamine, 2-hydroxyethyl-2-hydroxytetradecylamine, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, di-2-hydroxyethyl-2-hydroxydodecylamine , Alkyl (C 18-18) benzyldimethylammonium chloride, ethylene bisalkyl (C 18-18) amide, stearyl diethanolamide, lauryl diethanolamide, myristyl diethanolamide, palmi Le diethanolamide, and the like. Of these, amine compounds or amide compounds having a hydroxyalkyl group are preferably used. In the present invention, two or more of these compounds may be used in combination.

The lens composition according to the present invention preferably contains a compound having a hydrophilic group and a hydrophobic group in the same molecule in an amount of 0.01 to 1 based on 100 parts by weight of the cyclic olefin resin.
0 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.3 to 3 parts by weight.

The lens composition according to the present invention as described above may optionally contain other components together with the cyclic olefin resin and the compound as long as the object of the present invention is not impaired. , Additives other than the above compounds, such as heat stabilizers, stabilizers such as weathering stabilizers, crosslinking agents,
It may contain a crosslinking assistant, an antistatic agent, a slip agent, an anti-blocking agent, an anti-fogging agent, a lubricant, a dye, a pigment, a mineral oil-based softener, a petroleum resin, a wax and the like.

Specifically, as a stabilizer contained as an optional component, for example, tetrakis [methylene-3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate]
Methane, β- (3,5-di-t-butyl-4-hydroxyphenyl)
Propionic acid alkyl ester, 2,2'-oxazamide bis [ethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl)
Examples include phenolic antioxidants such as propionate, and fatty acid metal salts such as zinc stearate, calcium stearate and calcium 1,2-hydroxystearate. These can be used in combination. For example, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is used in combination with zinc stearate or calcium stearate. Can also.

As stabilizers, for example, distearyl pentaerythritol diphosphite, di (nonylphenyl) pentaerythritol diphosphite, phenyl-4,4'-isopropylidene diphenol-pentaerythritol diphosphite, bis (2, 4-di-t-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, phenylbisphenol-
A-pentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) phosphite, tris (nonylphenyl) phosphite, tetrakis (2,4-
Phosphorus stabilizers such as di-t-butylphenyl) -4,4'-biphenylenediphosphite and bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite can also be used. it can.

Further, the lens composition of the present invention may contain an organic filler or an inorganic filler as needed, as long as the object of the present invention is not impaired. For example, silica, diatomaceous earth, Alumina, titanium oxide, magnesium oxide, pumice powder, pumice balloon, aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, dolomite, calcium sulfate, potassium titanate, barium sulfate, calcium sulfite, talc, clay, mica, asbestos, It may contain glass flakes, glass beads, calcium silicate, montmorillonite, bentonite, graphite, aluminum powder, molybdenum sulfide, and the like.

In the objective lens according to the tenth aspect, 0.5 ≦ D / f ≦ 0.7 (1) is established between the focal length f and the lens outer diameter D. A compact and compact DVD that can be obtained as a small and high-precision lens required as an objective lens of a compatible optical pickup device while having a high-precision diffraction surface and having high-performance optical characteristics while retaining high-performance optical characteristics. A / CD compatible optical pickup device can be realized.

In the objective lens according to the eleventh aspect of the present invention, 0.45 ≦ t / f ≦ 0.73 (2) is established between the axial thickness t and the focal length f. A compact and compact DVD that can be obtained as a small and high-precision lens required as an objective lens of a compatible optical pickup device while having a high-precision diffraction surface and having high-performance optical characteristics while retaining high-performance optical characteristics. A / CD compatible optical pickup device can be realized.

According to a twelfth aspect of the present invention, the diffractive surface has a plurality of orbicular zones, and the total number of orbicular zones is 13 or more and 50 or less. 13-5 ring zones on the diffraction surface
Since it is 0, it is easy to manufacture a molding die, and it is possible to obtain an objective lens for a DVD / CD five-way optical pickup device having a diffraction surface having a desired shape and a high diffraction effect.

An objective lens according to a thirteenth aspect is characterized in that the objective lens has an optical function part and a flange formed on the outer periphery thereof, and the flange has a notch.

The objective lens according to claim 14, wherein the notch is a portion obtained by cutting a part of a substantially circular outer peripheral surface of the flange portion when viewed in the optical axis direction. .

The objective lens according to the fifteenth aspect is characterized in that a part of the image side surface has a surface extending in a direction substantially perpendicular to the optical axis.

FIG. 11 is a sectional view (FIG. 11A) and a front view (FIG. 11B) showing the objective lens of the present invention. In FIG. 11, the objective lens OL has a lens part OL1 as an optical function part and a flange part OL2 formed around the lens part OL1. The flange OL2 is provided with a notch Gt. In FIG. 11, the notch Gt
Is an arc shape, but may be, for example, an arc shape or a straight shape in the opposite direction. Although not shown in FIG. 11, a diffraction ring zone having the above-described configuration is provided on the optical surface of the lens unit OL.

That is, the notch Gt may be a portion obtained by cutting a part of the substantially circular outer peripheral surface of the flange portion when viewed from the optical axis direction. The reason why the notch Gt is provided in this way is to grasp the optimum rotation angle in relation to the position of the gate because the optical characteristic changes in the rotation direction depending on the position of the resin gate when the resin lens is molded. is there. In particular, it is preferable to provide a notch Gt at the position of the gate because the position of the gate can be easily determined and the optimum rotation angle can be grasped.

Further, the objective lens OL has a flange OL
2, a surface OL3 extending in a direction substantially perpendicular to the optical axis is provided on a part of the emission side surface (image side surface) of the information recording and / or reproduction light focused by the objective lens OL. Provided. By providing such a surface OL3, the objective lens OL can be accurately maintained perpendicular to the optical axis.

A DVD / CD compatible optical pickup device according to a sixteenth aspect comprises at least two light sources having different wavelengths from each other and an objective lens for condensing a light beam from the light source on a recording surface of a DVD or a CD. Condensing optical system including, and light receiving means for detecting reflected light from the recording surface, the objective lens has a diffraction surface, is formed using a composition containing an olefin-based resin It is characterized by having. Since the olefin-based resin has been described in detail, the description is omitted. Further, the description of the same effect as the effect described in relation to the objective lens of the present invention will be omitted.

A DVD / CD compatible optical pickup device according to the present invention comprises at least two light sources having different wavelengths from each other and an objective lens for condensing a light beam from the light source on a recording surface of a DVD or a CD. The objective lens has a diffraction surface, and the melt flow rate MFR is 30 to 60 (g / 10 min.). The composition is characterized by being formed using a composition that satisfies (1).

A DVD / CD compatible optical pickup device according to claim 18 comprises at least two light sources having different wavelengths from each other and an objective lens for condensing a light beam from the light source on a recording surface of a DVD or CD. A condensing optical system, and a light receiving unit for detecting light reflected from the recording surface, wherein the objective lens has a diffractive surface, and is exposed at an environmental temperature of 80 ° C. and a humidity of 90% for 48 hours; After that, after leaving the room for 3 hours, when the light beam having the wavelength of 650 nm and the outer diameter of 1 mm is irradiated, the transmittance is reduced by 6% or less.

The DVD / CD compatible optical pickup device according to the nineteenth aspect is characterized in that the objective lens is formed using a composition containing an olefin resin.

A DVD / CD compatible optical pickup device according to claim 20, wherein the objective lens is formed using a composition satisfying a melt flow rate MFR of 30 to 60 (g / 10 minutes). Features.

A DVD / CD compatible optical pickup device according to claim 21 is characterized in that the composition contains an olefin resin.

The DVD / CD compatible optical pickup device according to claim 22 is characterized in that the olefin resin is a cyclic olefin resin.

The DVD / CD compatible optical pickup device according to claim 23, wherein the cyclic olefin resin has at least one repeating unit selected from the following [A-1] to [A-3]. And [A-1] a random copolymer of ethylene and a cyclic olefin represented by the above chemical formula [Formula 1] or [Formula 2]; (In the chemical formula [Formula 1], n is 0 or 1, and m
Is 0 or a positive integer; q is 0 or 1;
^{1 to} R ¹⁸ and R ^a and R ^b are each independently a hydrogen atom, a halogen atom or a hydrocarbon group optionally substituted with halogen, and R ^{15 to} R ¹⁸ are bonded to each other to form a monocyclic or polycyclic ring. And the monocyclic or polycyclic ring may have a double bond, and may form an alkylidene group with R ¹⁵ and R ¹⁶ or with R ¹⁷ and R ^18. You may. (In the chemical formula [Formula 2], p and q are 0 or a positive integer, m and n are 0, 1 or 2, and R ^{1 to} R ¹⁹ are each independently a hydrogen atom, a halogen atom, a halogen atom, And a carbon atom to which R ⁹ or R ¹⁰ is bonded, a carbon atom to which R ¹³ is bonded, or a carbon atom to which R ¹¹ is bonded. May be bonded directly or via an alkylene group having 1 to 3 carbon atoms, and n = m =
When 0, R ¹⁵ and R ¹² or R ¹⁵ and R ¹⁹ may combine with each other to form a monocyclic or polycyclic aromatic ring. [A-2] A ring-opened polymer or copolymer of a cyclic olefin represented by the chemical formula [Chemical Formula 1] or [Chemical Formula 2], and [A-3] The ring-opened polymer or copolymer. Combined [A-2]
Hydride.

A DVD / CD compatible optical pickup device according to claim 24 is characterized in that the composition contains a compound having a hydrophilic group and a hydrophobic group in the same molecule.

According to a twenty-fifth aspect of the present invention, in the DVD / CD compatible optical pickup device, in the objective lens, 0.5 ≦ D / f ≦ 0.7 (focal length f and lens outer diameter D). 1) is satisfied.

In the DVD / CD compatible optical pickup device according to the twenty-sixth aspect, the distance between the outer diameter Do of the objective lens and the effective diameter De is 0.4 mm ≦ Do−De ≦ 3.0 mm. Is satisfied, a small and high-precision lens required as an objective lens of a DVD / CD compatible optical pickup device is reduced in weight and cost while having a high-precision diffraction surface and having high-performance optical characteristics. Thus, a compact DVD / CD compatible optical pickup device can be realized.

The DVD / CD compatible optical pickup device according to claim 27, wherein the end thickness of the objective lens is 0.9 m.
m or less, a more compact DVD / CD compatible optical pickup device can be provided.

A DVD / CD compatible optical pickup device according to claim 28, wherein 0.45 ≦ t / f ≦ 0.73 (2) between the axial thickness t of the objective lens and the focal length f. ) Holds true.

A DVD / CD compatible optical pickup device according to claim 29, wherein the diffraction surface has a plurality of orbicular zones, and the total number of orbicular zones is 13 or more and 50 or less.

A DVD / CD compatible optical pickup device according to claim 30, wherein the objective lens comprises: an optical function unit;
And a flange formed on the outer periphery thereof, wherein the flange has a notch.

According to a thirty-first aspect of the present invention, in the DVD / CD compatible optical pickup device, the notch is a portion obtained by cutting a part of a substantially circular outer peripheral surface of the flange portion when viewed in the optical axis direction. It is characterized by the following.

A DVD / CD compatible optical pickup device according to claim 32, wherein a part of the image side surface of the objective lens is
It has a surface extending in a direction substantially perpendicular to the optical axis.

In the objective lens according to the thirty-third aspect, when the optical path difference function of the diffractive surface is φ (h) (h is a distance from the optical axis), dφ (h) / dh at a predetermined distance h. Are discontinuous or substantially discontinuous.

In an optical system of an optical pickup device for recording / reproducing information with respect to a plurality of types of optical information recording media having different thicknesses, a light flux outside a predetermined numerical aperture is used in a use state where a numerical aperture NA is small. With a flare, a small numerical aperture NA
Without using the aperture restriction for the above, a relatively large spot diameter can be obtained without excessively narrowing the beam diameter. Thus, by using an objective lens provided with a diffraction ring zone as in the present invention, it is possible to provide an optical pickup device for recording and reproducing information on a plurality of types of optical information recording media having different thicknesses. Become.

It is desirable that the flare be a sufficiently large flare outside the predetermined numerical aperture. If the flare amount is insufficient, it adversely affects a spot in a portion necessary for information recording or reproduction. On the other hand, according to the present invention, the spherical aberration outside the predetermined numerical aperture can be made a sufficiently large flare in the use state where the numerical aperture NA is small. In other words, the spherical aberration is made substantially discontinuous in the state of use on the side where the NA is small, a well-squeezed spot is obtained inside the predetermined numerical aperture, and the light beam outside that becomes a large flare for recording and reproduction. The necessary spots are not affected.

The optical path difference function φ (h) represents the optical path difference added by the diffractive surface to the first-order diffracted light of the reference wavelength. Each time the value of the optical path difference function changes by mλ (m is the diffraction order), the diffraction ring is changed. A belt is provided. The reference wavelength is a wavelength at which the diffraction efficiency is maximized.

Here, at a position at a certain distance h from the optical axis, d
When φ (h) / dh is substantially discontinuous, dφ (h) / d
Even when h is a continuous function, it refers to a state in which the pitch of the diffraction ring zone changes abruptly when the pitch of the diffraction ring zone is obtained from the optical path difference function. Preferably, | d ² φ (h) /
dh ² | is large enough to satisfy 0.20 or more.

In the present specification, an orbicular zone (diffractive orbicular zone) is defined as a ring from step (step) to step (step) when a diffraction shape is viewed in a cross section parallel to the optical axis direction. Treated as a belt.

In the objective lens according to the thirty-fourth aspect, the width of the outermost orbicular zone formed inside the predetermined distance h in the direction perpendicular to the optical axis is adjacent to the outermost orbicular zone. And a width in a direction perpendicular to the optical axis in an annular zone formed outside the predetermined distance h.

FIG. 9 is a schematic diagram showing an example of a lens as an objective lens provided with a diffraction ring zone. In FIG.
The pitches and steps of the diffractive orbicular zones are drawn larger than they actually are for easy understanding, and the numbers thereof are also small for easy understanding. As a specific example of an objective lens having a diffraction surface formed with a ring-shaped pattern (diffraction ring zone) composed of a plurality of ring zones, for example, Japanese Patent Application Laid-Open No.
Reference can be made to JP-A-18.

The left optical surface of the lens 3 shown in FIG. 9 has an optical path difference function φ (h) where h is the distance from the optical axis X, and the optical path difference function φ at a predetermined distance h. The function dφ (h) / dh obtained by differentiating (h) has a point H at which the function dφ (h) / dh is discontinuous or substantially discontinuous. On the inner surface of point H,
The diffraction zones 3a to 3f are provided so as to gradually decrease the pitch (width in a direction perpendicular to the optical axis) along the mother aspheric surface B, and on the outer surface of the inflection point H, The diffraction zones 3g to 3i are provided along the mother aspheric surface B so as to gradually reduce the pitch. In addition, the mother aspheric surface B also has a point H.
Is bent or substantially bent.

Here, at the point H, the pitch of the diffraction zones changes. More specifically, the pitch gradually decreases in the diffraction zones 3a to 3f, but the pitch P1 of the diffraction zone 3f closest to the point H inside the point H is in contact with the diffraction zone 3f, and Pitch P of 3 g of diffraction zone outside point H
It is smaller than 2. In this way, the point H
Of light having a predetermined wavelength passing outside the lens can be effectively converted to flare light.

In the objective lens according to the thirty-fifth aspect, when the CD is irradiated with light from a light source having a wavelength λ located at a predetermined object distance, the wavefront aberration is 0.1 mm at a numerical aperture NA equal to or less than the predetermined distance h. 07λrms or less, and the spherical aberration of the light beam passing inside the predetermined distance h is 10λ-100
λ is small.

As described above, if the spherical aberration of the light beam passing inside the predetermined distance h is smaller than the spherical aberration of the light beam passing outside the predetermined distance h by 10λ to 100λ, the predetermined distance h is Light rays passing outside can be regarded as flares, and it is preferable that the beam diameter is not excessively narrowed and a relatively large spot diameter can be obtained without using an aperture limit for a small numerical aperture NA.

An objective lens according to a thirty-sixth aspect is characterized in that a certain i-th diffraction ring zone satisfies the following expression, counted from the optical axis to the peripheral direction of the diffraction surface. 1.2 ≦ p _{i + 1} / p _i ≦ 10 (4) where p _{i is} the width of the i-th diffraction ring zone counted from the optical axis in the peripheral direction in the direction perpendicular to the optical axis.

It is to be noted that the above-mentioned i-th diffraction zone is preferably the 14th to 22nd zones, where 1 is the zone on the optical axis.

According to the thirty-sixth aspect of the present invention, the numerical aperture NA
In the use state on the side where is small, the spherical aberration outside the predetermined numerical aperture can be made a sufficiently large flare. That is,
The spherical aberration is made substantially discontinuous in the use state on the side where the NA is small, a well-focused spot is obtained inside a predetermined numerical aperture, and the light beam outside that becomes a large flare and is necessary for recording and reproduction. It does not affect the spot of the part. If the value p _{i + 1} / p _i is equal to or larger than the lower limit of the equation (4), a sufficient flare can be obtained. On the other hand, the value p _{i + 1}
When / p _i is equal to or less than the upper limit value of the expression (4), the zone pitch is not too small, and the production of the diffraction surface becomes easy.

The objective lens according to claim 37 has NA
The number m of the diffraction ring zone through which the light ray of 0.60 passes satisfies 22 ≦ m ≦ 32 (5). However, the number of the diffraction ring zone is 1 on the ring zone on the optical axis, and it is counted outward in order.

According to the thirty-seventh aspect of the present invention, when the number m is equal to or larger than the lower limit of the equation (5), the spherical aberration caused by the substrate thickness of the optical information recording medium (for example, CD and DVD). Can be sufficiently corrected. On the other hand, if the number m is equal to or less than the upper limit of the expression (5), there is an advantage that a lens having good diffraction efficiency can be easily formed.

An objective lens according to a thirty-eighth aspect of the present invention is characterized in that the light beam is incident as a substantially parallel light beam within a wavelength range of 630 to 665 nm.

An objective lens according to claim 39 is a DVD
The wavelength for CD is λ1, the wavelength for CD is λ2 (λ1 <λ2), the required numerical aperture on the image side required for recording or reproducing a DVD is NA1 by the luminous flux of the wavelength λ1, and the wavelength λ2 , The required numerical aperture on the image side required for recording or reproducing a CD is set to NA2 (NA1 ≧ NA).
2), the wavefront aberration is 0.07λ1 with respect to the combination of the wavelength λ1, the DVD, and the required numerical aperture NA1.
rms or less, and the wavefront aberration is not more than 0.1 for the combination of the wavelength λ2, CD and the required numerical aperture NA2.
A light beam having a wavelength of not more than 07λ2 rms and having a required numerical aperture NA2 or more for a combination of the wavelength λ2 and the CD is flare.

In the objective lens according to the forty-ninth aspect, when light is irradiated from a light source having the wavelength λ2 at a predetermined object distance to the CD, the light beam having the required numerical aperture of NA2 or more and NA1 or less can record the CD. On the surface, it is distributed in the range of the diameter w2 or more and w1 or less, and satisfies 10 μm ≦ w2 ≦ 50 μm (6) 20 μm ≦ w1−w2 ≦ 110 μm (7).

If the diameter w2 is equal to or larger than the lower limit of the equation (6), a beam diameter equivalent to that of an ideal lens having a numerical aperture NA2 can be obtained for an optical information recording medium having a transparent substrate thickness t2.
The light flux of A2 or more becomes a flare and is less likely to adversely affect the writing and / or reading of information.

If the value (w1−w2) is equal to or larger than the lower limit of the equation (7), the light flux having a numerical aperture NA2 or more becomes a wide-area flare with respect to the optical information recording medium having the transparent substrate thickness t2. A signal can be obtained.

When the diameter W2 is equal to or less than the upper limit of the equation (6),
And when the value (w1−w2) is equal to or less than the upper limit of Expression (7), in the case of an objective lens made of a plastic lens, the deterioration of the spherical aberration due to the change in the refractive index due to the temperature change is caused by the oscillation wavelength of the semiconductor laser accompanying the temperature change Can be compensated to some extent by a change in spherical aberration caused by a diffractive surface utilizing the change in. Increasing the flare for a light beam having a numerical aperture of NA2 or more is equivalent to weakening the effect of diffraction for correcting spherical aberration due to the thickness of the substrate. It is not preferable to make the flare too large, as it will impair.

In the objective lens according to the forty-first aspect, when the CD is irradiated with light from the light source of the wavelength λ2 at a predetermined object distance, the wavefront aberration is 0 at the numerical aperture NA of the predetermined distance h or less. .07λ2 rms or less, and the spherical aberration of the light beam passing inside the predetermined distance h is 10 times smaller than the spherical aberration of the light beam passing outside the predetermined distance h.
λ2 to 100λ2 are small.

The objective lens according to claim 42, wherein the wavelength λ1 is a wavelength in the range of 630 to 665 nm and the wavelength λ2 is a wavelength in the range of 750 to 810 nm. It is suitable for a DVD / CD compatible optical pickup device capable of recording and / or reproducing information.

A DVD / CD compatible optical pickup device according to claim 43, wherein the optical path difference function of the diffraction surface is φ (h)
Where h is the distance from the optical axis, dφ (h) / dh is a discontinuous or substantially discontinuous function at a predetermined distance h.

A DVD / CD compatible optical pickup device according to a forty-fourth aspect, wherein a width in a direction perpendicular to the optical axis of an outermost ring zone among the ring zones formed inside the predetermined distance h is the outermost ring zone. And the predetermined distance h
Is smaller than the width in the direction perpendicular to the optical axis in the annular zone formed outside of.

A DVD / CD compatible optical pickup device according to claim 45, wherein when the CD is irradiated with light from a light source having a wavelength λ at a predetermined object distance via the objective lens, the predetermined distance h is applied. At the following numerical aperture NA, the wavefront aberration is 0.07 λrms or less, and the spherical aberration of the light beam passing inside the predetermined distance h is 10 λ more than the spherical aberration of the light beam passing outside the predetermined distance h. ~ 100λ
It is characterized by being small.

A DVD / CD compatible optical pickup device according to claim 46 is characterized in that a certain i-th diffraction ring zone satisfies the following expression, counting from the optical axis to the peripheral direction of the diffraction surface. 1.2 ≦ p _{i + 1} / p _i ≦ 10 (4) where p _{i is} the width of the i-th diffraction ring zone counted from the optical axis in the peripheral direction in the direction perpendicular to the optical axis.

A DVD / CD compatible optical pickup device according to claim 47 is characterized in that the number m of the diffraction ring zone through which the light beam of NA 0.60 passes satisfies 22 ≦ m ≦ 32 (5).

A DVD / CD compatible optical pickup device according to claim 48, wherein the wavelength of the light source for DVD is λ1, and the wavelength of the light source for CD is λ2 (λ1 <λ).
2), the light flux of the wavelength λ1 is used to set the required numerical aperture on the image side required for recording or reproducing a DVD to be NA1, and the light flux of the wavelength λ2 is used for recording or reproducing a CD. The required numerical aperture on the image side is NA2 (NA1 ≧
NA2), the wavefront aberration is 0.07 with respect to the combination of the wavelength λ1, the DVD and the required numerical aperture NA1.
λ1 rms or less, and the wavefront aberration is 0.07 λ2 rms or less for the combination of the wavelength λ2, CD and the required numerical aperture NA2, and the required numerical aperture for the combination of the wavelength λ2 and CD. It is characterized in that luminous flux of NA2 or more is made to be a flare.

The DVD / CD compatible optical pickup device according to claim 49, wherein when the CD is irradiated with light from the light source of the wavelength λ2 at a predetermined object distance via the objective lens, the required aperture is adjusted. A light beam having a number NA2 or more and NA1 or less is distributed on a recording surface of a CD in a range of a diameter w2 or more and w1 or less, and satisfies 10 μm ≦ w2 ≦ 50 μm (6) 20 μm ≦ w1−w2 ≦ 110 μm (7) I do.

The DVD / CD compatible optical pickup device according to claim 50, wherein the object point of said objective lens with respect to the combination of said wavelength λ1 and DVD, and said wavelength λ2 and CD
The object point of the objective lens with respect to the combination of (1) is at an optically equal distance.

A DVD / CD compatible optical pickup device according to claim 51, wherein said wavelength λ1 is 630-665n.
m, and the wavelength λ2 is 750 to 750.
The wavelength is in the range of 810 nm.

In the objective lens according to the fifty-second aspect, the amount of spherical aberration when a light beam having a wavelength λ having a numerical aperture NA in the range of 0.5 to 0.7 passes through the objective lens is less than 0.5. It is characterized in that the amount of spherical aberration when the light beam having the wavelength λ passes is larger by 10λ to 100λ or more.

A DVD / CD compatible optical pickup device according to claim 53, wherein the objective lens has a spherical aberration amount when a light beam having a wavelength λ having a numerical aperture NA in the range of 0.5 to 0.7 passes through the objective lens. Is smaller than the spherical aberration amount when a light beam having a wavelength λ with a numerical aperture NA of less than 0.5 passes therethrough.
It is characterized by being larger than λ to 100λ. The optical pickup device is configured such that, in at least one of the diffraction zones on the surface of the objective lens, a width in a direction perpendicular to the optical axis of an outermost zone among the zones formed inside the predetermined distance h is the most. Adjacent to the outer orbicular zone and at the predetermined distance h
Is smaller than the width in the direction perpendicular to the optical axis in the annular zone formed outside of.

A DVD / CD compatible optical pickup device according to claim 54, wherein, when a light beam having a numerical aperture NA of less than 0.5 passes through the objective lens, the light beam reflected from the CD receives the light beam from the light receiving means. When a light beam having a numerical aperture NA of 0.5 or more passes through and is irradiated toward the light receiving means so as to be included in the light receiving surface, the light beam reflected from the CD is:
The light is radiated to the surroundings except for the light receiving surface of the light receiving means.

55. A DVD / CD compatible optical pickup device according to claim 55, wherein said light receiving means has one to three substantially rectangular light receiving surfaces, and said numerical aperture NA is 0.5 or more. The spot diameter of the light beam on the recording surface of the CD is 5
μm or more.

A DVD / CD compatible optical pickup device according to claim 56, wherein said light receiving means has three rectangular light receiving surfaces arranged substantially on a straight line, and said numerical aperture NA is equal to 0.1.
The spot diameter of the light beam of 5 or more on the recording surface of the CD is 25 μm.
m or more.

The DVD / CD compatible optical pickup device according to claim 57, wherein the objective lens has a required numerical aperture NA.
When a light flux of 0.5 or more passes, the light flux reflected from the CD is irradiated toward the light receiving means so as to include only the peripheral light receiving surface.

A DVD / CD compatible optical pickup device according to claim 58, wherein said light receiving means has at least two stripe-shaped light receiving surfaces, and said numerical aperture NA is 0.5.
The spot diameter of the above light beam on the recording surface of the CD is 20 μm.
It is characterized by the above.

A DVD / CD compatible optical pickup device according to claim 59, wherein said light receiving means has at least four stripe-shaped light receiving surfaces, and said numerical aperture NA is 0.5.
The spot diameter of the light beam on the recording surface of the above CD is 50 μm.
It is characterized by the above.

Regarding the light receiving means used in the optical pickup device, there are a case where a module in which the laser light source and the light receiving means are unitized is used, and a case where the laser light source and the light receiving means are separately provided. The former will be referred to as integrated light receiving means, and the latter will be referred to as separate light receiving means. FIG. 8A is a schematic diagram illustrating a light receiving surface of the integrated light receiving device, and FIG. 8B is a schematic diagram illustrating a light receiving surface of the separate light receiving device. In FIG. 8B, the light receiving surface of the light receiving means, which is generally composed of approximately three rectangular light receiving surfaces, has a central light receiving surface CS and a pair of peripheral light receiving surfaces PS arranged on both sides thereof. are doing. Central light receiving surface C
S has a function of detecting whether or not a write and / or read error of a recording signal has occurred.
Has a function of detecting whether a tracking error has occurred.

In the present invention, a light flux having a wavelength λ having a numerical aperture NA of 0.5 or more is applied to an optical information recording medium having a small required numerical aperture, that is, a CD, of two optical information recording media of DVD and CD. When passed through the objective lens,
Flare is formed by the diffraction surface. As shown in FIG. 8B, a light beam having a wavelength λ having a numerical aperture NA of less than 0.5 forms a spot at the center of the central light receiving surface CS. The light beam is emitted as flare light having an inner diameter of φ1. At this time, if the inner diameter φ1 is sufficiently large and completely encloses the central light receiving surface CS, a light beam with a wavelength λ having a numerical aperture NA of 0.5 or more is irradiated only on the peripheral light receiving surface PS, Unnecessary light is prevented from being detected on the central light receiving surface CS as the light receiving surface in the present invention, and erroneous detection can be prevented.

Further, the inner diameter of the flare light is set to φ larger than φ1.
2, the light flux having the wavelength λ having a numerical aperture NA of 0.5 or more is provided as the light receiving surface according to the present invention. In this case, unnecessary light is prevented from being detected, and erroneous detection can be prevented.

According to a fifty-fifth aspect of the present invention, there is provided a DVD / CD compatible optical pickup device, wherein the number of the light receiving means is one to three.
Number of light receiving surfaces having a substantially rectangular shape, the numerical aperture NA
If the spot diameter of the light flux of 0.5 or more on the recording surface of the CD is 5 μm or more, unnecessary light hardly enters the central light receiving surface CS in the separate light receiving means, thereby preventing erroneous detection. I can do it.

As in the DVD / CD compatible optical pickup device according to claim 56, the light receiving means has three rectangular light receiving surfaces arranged substantially in a straight line, and has a numerical aperture NA of 0.5 or more. The spot diameter of the light beam on the recording surface of the CD is 2
If it is 5 μm or more, it becomes more difficult for unnecessary light to enter the peripheral light receiving surface PS in the separate light receiving means, and erroneous detection can be further prevented.

On the other hand, as shown in FIG. 8A, the integrated light receiving means comprises at least two or more, usually four or more, stripe-shaped light receiving surfaces. Numerical aperture N
A light beam with a wavelength λ of less than 0.5 forms a spot between the central light receiving surface groups CS, while a light beam with a wavelength λ with a numerical aperture NA of 0.5 or more becomes flare light with an inner diameter φ1. Irradiated. At this time, if the inner diameter φ1 is sufficiently large and completely encloses the central light receiving surface group CS, the numerical aperture NA is set to 0.1.
A light beam having a wavelength λ of 5 or more is applied only to the peripheral light receiving surface PS, and unnecessary light is prevented from being detected in the central light receiving surface group CS as the light receiving surface according to the present invention.
False detection can be prevented.

As in the DVD / CD compatible optical pickup device according to claim 58, a CD having a light flux having at least two stripe-shaped light receiving surfaces and a numerical aperture NA of 0.5 or more.
If the spot diameter on the recording surface is 20 μm or more, it becomes difficult for unnecessary light to enter the central light receiving surface CS in the integrated light receiving means, and erroneous detection can be prevented.

Further, as in the DVD / CD compatible optical pickup device according to claim 59, the optical pickup device has at least four stripe-shaped light receiving surfaces and has a numerical aperture NA of 0.5 or more on the recording surface of a CD. If the spot diameter is 50 μm or more, unnecessary light hardly enters the peripheral light receiving surface PS in the integrated light receiving means, and erroneous detection can be further prevented.

The diffraction surface (or diffraction pattern) used in this specification is a surface (or form) provided with a relief on the surface of a lens so as to condense or diverge a light beam by diffraction. Say. As the shape of the relief, for example, a substantially concentric annular zone centered on the optical axis is formed on the surface of the lens, and each annular zone has a saw-like shape when viewed in a cross section on a plane including the optical axis. Is known,
It includes such a shape.

In the present specification, an objective lens is, in a narrow sense, a collection located at a position closest to the optical information recording medium and opposed to the optical information recording medium when the optical information recording medium is loaded in the optical pickup device. Refers to a lens that has a light effect,
In a broad sense, it refers to a lens group that can be operated at least in the optical axis direction by an actuator together with the lens. Here, such a lens group refers to at least one or more (eg, two) lenses. Therefore, in this specification, the numerical aperture NA of the objective lens on the optical information recording medium side (image side) indicates the numerical aperture NA of the lens surface of the objective lens closest to the optical information recording medium. . Further, in this specification, the required numerical aperture NA is a numerical aperture defined by the standard of each optical information recording medium,
Alternatively, for each optical information recording medium, the numerical aperture of an objective lens having diffraction-limited performance capable of obtaining a spot diameter necessary for recording or reproducing information according to the wavelength of a light source used is shown.

In this specification, a CD as an optical information recording medium is, for example, an optical disk of various CD systems such as CD-R, CD-RW, CD-Video, CD-ROM, and a DVD is a DVD-ROM. ROM, DVD
-Refers to various DVD-type optical disks such as RAM, DVD-R, DVD-RW, and DVD-Video.

In the present specification, a DVD / CD compatible optical pickup device is capable of recording and / or reproducing information on at least one kind of DVD among various DVD-type optical disks as described above. And an optical pickup device capable of recording or reproducing information on at least one type of CD among various CD-type optical disks as described above.
Of course, with such DVD / CD compatible functions,
This does not exclude an optical pickup device having a function of recording or reproducing information on an optical information recording medium other than D and CD.

As a preferred specific embodiment of the DVD / CD compatible optical pickup device, at least two light sources having different wavelengths are provided.
Using one light source with a certain wavelength in the range of ６６665 nm, and for CD using the other light source with a certain wavelength in the range of 750 to 810 nm, including the objective lens An optical pickup device configured to guide reflected light from a DVD or a CD to a light receiving unit via a converging light beam system.

The objective lens for a DVD / CD compatible optical pickup device is an objective lens that can be used for the DVD / CD compatible optical pickup device as described above.
Desirably, it is a single lens.

In this specification, the lens outer diameter D or the outer diameter Do of the objective lens is a substantially circular outer diameter of the entire objective lens including the flange portion when the objective lens is viewed in the optical axis direction. At this time, if a notch is provided on the outer periphery of the flange portion, the outer diameter is such that the notch is ignored.

The effective diameter De is the diameter on the side of the light source which is used substantially as an optical surface in the objective lens mounted on the optical pickup device. It is the maximum diameter of the area irradiated to the lens, centered on the optical axis.

Further, the end thickness is a thickness in the optical axis direction of the objective lens at a position on the surface of the objective lens corresponding to the effective diameter.

The optical pickup device of the present invention can be mounted on audio and / or image recording and / or reproducing devices such as various players or drives, or AV devices, personal computers, and other information terminals incorporating them. Can be.

In the DVD / CD compatible optical pickup device of the present invention, particularly, in an optical pickup device capable of reproducing only a DVD and a CD, the wavelength of the first laser light source for the DVD is set to λ1. When the wavelength of the second laser light source for CD is λ2, the imaging magnification mT1 of the objective lens with the laser light of the wavelength λ1 and the imaging magnification of the objective lens with the laser light of the wavelength λ2 mT
It is preferable that the following expressions hold for each of the two. −1/5 <mT1 <−1 / 7.5 (8) −1/3 <mT2 <−1 / 7.5 (9)

Further, as a DVD / CD compatible optical pickup device, particularly, in an optical pickup device capable of recording and reproducing a DVD and reproducing a CD only, the wavelength of the first laser light source for the DVD is set to λ1. Assuming that the wavelength of the second laser light source for CD is λ2, the imaging magnification mT1 of the objective lens for the laser light of the wavelength λ1 is different from that of the objective lens for the laser light of the wavelength λ2. Image magnification m
It is preferable that the following expressions be satisfied for T2. −1/3 <mT1 <− ／ (10) −1/5 <mT2 <− ／, 5 (11)

Further, as an optical pickup device compatible with DVD / CD, particularly, in an optical pickup device capable of only reproducing a DVD and recording and reproducing a CD, a DVD is used.
The wavelength of the first laser light source for CD
Assuming that the wavelength of the laser light source is λ2, the following expressions hold for the imaging magnification mT1 of the objective lens for the laser light of the wavelength λ1 and the imaging magnification mT2 of the objective lens for the laser light of the wavelength λ2. It is preferable to do so. −1/5 <mT1 <−1 / 7.5 (12) −1/3 <mT2 <− ／ (13)

Further, as an optical pickup device compatible with DVD / CD, particularly, an optical pickup device capable of only recording and reproducing a DVD and recording and reproducing a CD,
Assuming that the wavelength of the first laser light source for DVD is λ1 and the wavelength of the second laser light source for CD is λ2, the imaging magnification mT1 of the objective lens with the laser light of the wavelength λ1
And the imaging magnification mT2 of the objective lens with respect to the laser light having the wavelength λ2, it is preferable that the following expressions hold. −1/3 <mT1 <− ／ (14) −1/3 <mT2 <− ／ (15)

[0164]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The diffractive surface is represented by a mother aspherical surface having a macroscopic shape without the diffraction relief and an optical path difference function. The optical path difference function represents the optical path difference added by the diffraction surface to the first-order diffracted light of the reference wavelength, and a diffraction ring zone is provided every time the value of the optical path difference function changes by mλ (m is the diffraction order).

In the embodiment of the present invention, the base aspherical surface of the diffractive surface and the optical path difference function are defined by using the distance hb from the optical axis as a boundary.
The inside (optical axis side) and the outside (peripheral side) are represented by different functions.

At this time, in order to make the generating aspheric surface and the optical path difference function substantially continuous at the boundary hb, a constant term is provided for the outer generating aspheric surface and the outer optical path difference function. Optical path difference function Φ
(H) is represented by the following equation. Φ (h) = b0 + b2 * h 2 + b4 * h 4 + b6 * h 6 + ··· (16) However, h: distance from the optical axis b0, b2, b4, b6, ···: coefficients of the optical path difference function

On the other hand, the aspherical surface is represented by the following equation. ^{x = (h 2 / r)} / (1 + √ (1- (1 + k) h 2 / r 2)) + A0 + A2 * h 2 + A4 * h 4 + A6 * h 6 + ··· (17) However, A0, A2 , A4, A6, ...: aspherical coefficient k: conical coefficient r: paraxial radius of curvature r, d, n, and νd represent a radius of curvature of a lens, a surface interval, a refractive index at a reference wavelength, and an Abbe number.

When the above definition is used, the lens can be given power by setting the second order coefficient of the optical path difference function to a non-zero value. Also, a coefficient other than the second order of the optical path difference function, for example, a fourth order coefficient, a sixth order coefficient, an eighth order coefficient,
The spherical aberration can be controlled by setting the zero-order coefficient or the like to a value other than zero. Here, controlling means that the spherical aberration of the portion having the refracting power is corrected by generating the reverse spherical aberration, or that the entire spherical aberration is set to a desired value.

FIG. 1 is a schematic configuration diagram of an optical pickup device according to the present embodiment. In FIG. 1, a first light source 11 for recording and / or reproducing data on / from a first optical information recording medium (optical disc, for example, CD) and a recording light on a second optical information recording medium (optical disc, for example, DVD) are provided. And / or coupling lenses 21 and 22 for converting a divergence angle of a divergent light beam emitted from each light source into a desired divergence angle. A beam splitter 62 which is a light combining means for combining the light flux so as to travel in substantially one direction, an objective lens 3 for condensing the light flux from the beam splitter 62 on the information recording surface 5 of the optical information recording medium, Photodetectors 41 and 42 are provided as light receiving means for receiving light reflected from the recording medium. In the figure, 8 is an aperture, 9 is a cylindrical lens, 71 and 72 are quarter-wave plates, 1
Reference numeral 5 denotes a coupling lens for reducing the degree of divergence of a divergent light beam from the light source 11, 16 denotes a concave lens, and 17 denotes a hologram for separating a reflected light beam. As the objective lens 3, the objective lenses of Examples 1 to 3 were used.

The first light source 11 has a wavelength λ1 = 635 or 65.
A laser beam of about 5 nm is emitted, and at this time, the transparent substrate thickness t
The numerical aperture of the objective lens required for performing recording and / or reproduction on an optical information recording medium (DVD) of 1 = 0.6 mm is NA1 = 0.6 to 0.65. Second light source 12
Emits a laser beam having a wavelength of about λ2 = 785 nm. At this time, an optical information recording medium (C) having a transparent substrate thickness t2 = 1.2 mm is used.
The numerical aperture of the objective lens required to perform recording and / or reproduction for D) is set to NA2 = 0.5.

The role of the diffractive surface in order to obtain an objective lens which can be used for information recording media having different thicknesses with the single-element high NA objective lens of the present embodiment is to correct spherical aberration. Is corrected as follows.

In this embodiment, the thickness t1 of the transparent substrate
The position of the object point with respect to the recording medium and the thickness t2 of the transparent substrate
The position of the object point with respect to the recording medium of
For example, since collimated parallel light is incident on any of the objective lenses, spherical aberration due to a difference in substrate thickness is corrected only by the action of the diffractive surface. In the present embodiment, the spherical aberration is reduced to the range of the necessary numerical aperture NA2 for the recording medium having the thickness t2 of the transparent substrate, and the numerical aperture NA1 to the numerical aperture N
The range up to A2 increases the spherical aberration.

(Example 1) FIG. 2 is a sectional view of the objective lens of Example 1, and FIG. 3 is a spherical aberration diagram of the objective lens of Example 1. [Table 1] and [Table 2] show lens data of the objective lens of Example 1.

[0174]

[Table 1]

[Table 2]

Example 2 FIG. 4 is a cross-sectional view of the objective lens of Example 2, and FIG. 5 is a spherical aberration diagram of the objective lens of Example 2. [Table 3] and [Table 4] show lens data of the objective lens of Example 2.

[0176]

[Table 3]

[Table 4]

Example 2 FIG. 6 is a sectional view of the objective lens of Example 3, FIG. 7 is a spherical aberration diagram of the objective lens of Example 3, and FIG. FIG. 7B is an aberration diagram under information recording / reproduction conditions, and FIG. 7B is an aberration diagram under CD information recording / reproduction conditions. [Table 5] and [Table 6] show lens data of the objective lens of Example 3.

[0178]

[Table 5]

[Table 6]

Table 7 summarizes the data of Examples 1, 2 and 3 satisfying the above-mentioned conditional expressions.
Note that in the table, for example, p _i denotes the pitch at the i th annular zone.

[Table 7]

Incidentally, the lenses of Examples 1 to 3 were obtained by using the component [A]
Ethylene and tetracyclo [4.4.0.1 ^2,5 . Having a softening temperature (TMA) of 150 ° C. and an intrinsic viscosity [η] of 0.6 dl / g. 1 ^7,10 ] dodecene-3 (hereinafter T
100 parts by weight of a random copolymer with CD-3) and 2
0.6% of a mixture of -hydroxyethyl-2-hydroxydodecylamine and 2-hydroxyethyl-2-hydroxytetradodecylamine and 0.6% of pentaerythritol distearate, and further as other additives Tetrakis [methylene-3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate] methane is 0.6
Parts by weight were added, and the mixture was supplied to a twin-screw extruder in which the cylinder temperature was set at 250 ° C. and melt-kneaded to obtain a cyclic olefin-based resin composition.

Example 4 The lens of Example 4 had a softening temperature (TMA) of 150 ° C. as component [A].
Ethylene having an intrinsic viscosity [η] of 0.6 dl / g and tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodecene-3
100 parts by weight of a random copolymer (hereinafter referred to as TCD-3) and each component as shown in Table 8 as component [B] were added in the amounts (parts by weight) shown therein, and further other additives were added. As tetrakis [methylene-3- (3,5-di-t-butyl-4-
Hydroxyphenyl) propionate] methane is 0.6
Using a cyclic olefin-based resin composition obtained by adding a part by weight, feeding the mixture to a twin-screw extruder having a cylinder temperature set at 250 ° C., and kneading the mixture, using lens data similar to the lens data of Example 1, Certain lenses 1-4 were manufactured. Further, as a comparative example, a lens having similar lens data was manufactured using PMMA.

[Table 8]

The MFR of the comparative lens and the lens 4 of the present invention,
The refractive index, water absorption, and heat resistance temperature were measured. Table 9 shows the results.
Shown in

[Table 9]

The lens 4 has a water absorption of 0.01% or less, which is much smaller than that of the comparative lens, and has a high heat-resistant temperature, so that it is unlikely that the refractive index changes or deteriorates due to environmental changes. You can see that there is. Also, lens 4
Since the refractive index of the lens is larger than that of the comparative lens, the end thickness of the lens can be increased, the moldability of the lens can be improved, and the transferability can be improved. In addition, the transferability can be improved because the melt flow rate MFR is large. Therefore, in the case of a lens that is small and requires high precision, such as an objective lens of an optical pickup device, it is possible to reduce the incidence of defective products during lens manufacturing, and to reduce the cost.

Further, the values of the lenses 1 to 4 measured at a transmittance of 90 ° C. and a humidity of 90% were obtained from the values of the transmittance measured by a transmittance tester.
Exposure for 8 hours, and after leaving the room for 3 hours, the transmittance reduction (%), which is the value obtained by subtracting the value of the transmittance measured again by the transmittance tester, is shown in [Table 10].

[Table 10]

FIG. 10 is a schematic diagram showing a transmittance tester performed by the present inventors. In FIG. 10, the jig 102
The two objective lenses 0L related to the lenses 1 to 4 are held back-to-back, and 65 mm from the laser light source 101 along the optical axis.
A luminous flux of φ1 mm having a wavelength of 0 nm is passed through an objective lens O
Spectroscopic altimeter 1 that transmits L and OL and is arranged on the opposite side
At 03, the light intensity was determined.

[0186]

According to the present invention, a DVD / CD compatible optical pickup device having small, light and inexpensive optical characteristics, having stable optical characteristics against environmental changes, small loss of light quantity, can be obtained. And a DVD / CD compatible optical pickup device using the objective lens can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical pickup device according to an embodiment.

FIG. 2 is a cross-sectional view of the objective lens of Example 1.

FIG. 3 is a diagram of spherical aberration in the objective lens of Example 1;

FIG. 4 is a sectional view of an objective lens according to a second embodiment.

FIG. 5 is a diagram of spherical aberration in the objective lens of Example 2;

FIG. 6 is a sectional view of an objective lens according to a third embodiment.

FIG. 7 is a diagram of spherical aberration in the objective lens of Example 3;

FIG. 8A shows a light receiving surface of an integrated light receiving means,
FIG. 8B is a schematic diagram showing the light receiving surface of the separate light receiving means.

FIG. 9 is a schematic diagram showing an example of a lens as an objective lens provided with a diffraction ring zone.

FIG. 10 is a schematic diagram showing a transmittance tester.

11 is a sectional view showing the objective lens of the present invention (FIG. 11)
(A)) and a front view (FIG. 11 (b)).

[Explanation of symbols]

 Reference Signs List 8 stop 9 cylindrical lens 11 first light source 12 second light source 15 coupling lens 16 concave lens 17 hologram 21, 22 coupling lens 41, 42 photodetector 62 beam splitter 71, 72 quarter-wave plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 3/08 G02B 3/08 G11B 7/12 G11B 7/12 7/135 7/135 A F term (reference ) 2H087 KA13 PA01 PA17 PB01 QA02 QA07 QA14 QA34 RA46 RA47 UA01 4J032 CA34 CA35 CA43 CA45 CA53 CB11 CF03 CG02 4J100 AA02P AR09Q AR11Q BC43Q BC44Q BC48Q BC49Q CA04 5D119 AA41 J01 FA01 EC01 J01 FA05

Claims (59)

[Claims] 1. An objective lens for a DVD / CD compatible optical pickup device, wherein the objective lens has a diffraction surface and is formed using a composition containing an olefin-based resin. 2. An objective lens used in a DVD / CD compatible optical pickup device, which is formed using a composition having a diffractive surface and having a melt flow rate MFR of 30 to 60 (g / 10 minutes). An objective lens characterized in that: 3. An objective lens used in a DVD / CD compatible optical pickup device, which has a diffractive surface, is exposed to an environment temperature of 80 ° C. and a humidity of 90% for 48 hours, and then indoors.
An objective lens characterized in that the transmittance is reduced by 6% or less when irradiated with a light beam having a wavelength of 650 nm and an outer diameter of 1 mm after being left for a time. 4. The objective lens according to claim 3, wherein the objective lens is formed using a composition containing an olefin-based resin. 5. The objective lens according to claim 3, wherein the objective lens is formed using a composition satisfying a melt flow rate MFR of 30 to 60 (g / 10 minutes). 6. The objective lens according to claim 2, wherein the composition contains an olefin-based resin. 7. The objective lens according to claim 1, wherein the olefin resin is a cyclic olefin resin. 8. The cyclic olefin resin according to the following [A]
The objective lens according to claim 7, comprising at least one repeating unit selected from [-1] to [A-3]. [A-1] A random copolymer of ethylene and a cyclic olefin represented by the following chemical formula [Formula 1] or [Formula 2]; (In the chemical formula [Formula 1], n is 0 or 1, and m is 0
Or a positive integer, q is 0 or 1, and R ¹ to
R ¹⁸ and R ^a and R ^b are each independently a hydrogen atom, a halogen atom or a hydrocarbon group optionally substituted with halogen, and R ^{15 to} R ¹⁸ are bonded to each other to form a monocyclic or polycyclic ring And the monocyclic or polycyclic ring may have a double bond, and may form an alkylidene group with R ¹⁵ and R ¹⁶ or with R ¹⁷ and R ^18. Good. Embedded image (In the chemical formula [Formula 2], p and q are 0 or a positive integer, m and n are 0, 1 or 2, and R ^{1 to} R
^{And 19} independently represent a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group optionally substituted with halogen, and a carbon atom to which R ⁹ or R ¹⁰ is bonded;
^The carbon atom to which ¹³ is bonded or the carbon atom to which R ¹¹ is bonded may be bonded directly or via an alkylene group having 1 to 3 carbon atoms. When n = m = 0, R ¹⁵
And R ¹² or R ¹⁵ and R ¹⁹ may combine with each other to form a monocyclic or polycyclic aromatic ring. [A-2] A ring-opened polymer or copolymer of a cyclic olefin represented by the chemical formula [Chemical Formula 1] or [Chemical Formula 2], and [A-3] The ring-opened polymer or copolymer. Combined [A-2]
Hydride. 9. The objective lens according to claim 1, wherein the composition contains a compound having a hydrophilic group and a hydrophobic group in the same molecule. 10. The method according to claim 1, wherein 0.5 ≦ D / f ≦ 0.7 is satisfied between the focal length f and the lens outer diameter D. Objective lens. 11. The method according to claim 1, wherein 0.45 ≦ t / f ≦ 0.73 is satisfied between the axial thickness t and the focal length f. Objective lens. 12. The objective lens according to claim 1, wherein the diffraction surface has a plurality of orbicular zones, and the total number of orbicular zones is 13 or more and 50 or less. 13. The objective lens according to claim 1, wherein the objective lens has an optical function portion and a flange formed on an outer periphery thereof, and the flange has a notch. 14. The notch, when viewed in the optical axis direction,
The objective lens according to claim 13, wherein a part of a substantially circular outer peripheral surface of the flange portion is a cut portion. 15. The image processing apparatus according to claim 1, wherein a part of the image side surface has a surface extending in a direction substantially perpendicular to the optical axis.
15. The objective lens according to any one of items 14 to 14. 16. A condensing optical system including at least two light sources having different wavelengths from each other, an objective lens for condensing a light beam from the light source on a recording surface of a DVD or a CD,
Light receiving means for detecting reflected light from the recording surface, wherein the objective lens has a diffraction surface and is formed using a composition containing an olefin-based resin. DVD / CD compatible optical pickup device. 17. A condensing optical system including at least two light sources having different wavelengths from each other, and an objective lens for condensing a light beam from the light source on a recording surface of a DVD or a CD;
A light receiving unit for detecting light reflected from the recording surface, wherein the objective lens has a diffractive surface, and a composition having a melt flow rate MFR satisfying 30 to 60 (g / 10 minutes) is used. A DVD / CD compatible optical pickup device characterized by being formed by: 18. A condensing optical system including at least two light sources having different wavelengths from each other, an objective lens for condensing a light beam from the light source on a recording surface of a DVD or a CD,
Light receiving means for detecting light reflected from the recording surface, wherein the objective lens has a diffractive surface, is exposed at an environmental temperature of 80 ° C. and a humidity of 90% for 48 hours, and then left indoors for 3 hours. A DVD / CD compatible optical pickup device, characterized in that a decrease in transmittance when irradiated with a light beam having a wavelength of 650 nm and an outer diameter of 1 mm is 6% or less. 19. The DVD / CD compatible optical pickup device according to claim 18, wherein the objective lens is formed using a composition containing an olefin-based resin. 20. The DVD / CD compatible according to claim 18, wherein the objective lens is formed using a composition having a melt flow rate MFR satisfying 30 to 60 (g / 10 minutes). Optical pickup device. 21. The D according to claim 17, wherein the composition contains an olefin resin.
VD / CD compatible optical pickup device. 22. The olefin resin according to claim 16, wherein the olefin resin is a cyclic olefin resin.
22. A DVD / CD compatible optical pickup device according to any one of 21. 23. The DVD / CD compatible light according to claim 22, wherein the cyclic olefin-based resin has at least one repeating unit selected from the following [A-1] to [A-3]. Pickup device. [A-1] a random copolymer of ethylene and a cyclic olefin represented by the following chemical formula [formula 1] or [formula 2]; (In the chemical formula [Formula 1], n is 0 or 1, and m is 0
Or a positive integer, q is 0 or 1, and R ¹ to
R ¹⁸ and R ^a and R ^b are each independently a hydrogen atom, a halogen atom or a hydrocarbon group optionally substituted with halogen, and R ^{15 to} R ¹⁸ are bonded to each other to form a monocyclic or polycyclic ring And the monocyclic or polycyclic ring may have a double bond, and may form an alkylidene group with R ¹⁵ and R ¹⁶ or with R ¹⁷ and R ^18. Good. Embedded image (In the chemical formula [Formula 2], p and q are 0 or a positive integer, m and n are 0, 1 or 2, and R ^{1 to} R
^{And 19} independently represent a hydrogen atom, a halogen atom, a hydrocarbon group or an alkoxy group optionally substituted with halogen, and a carbon atom to which R ⁹ or R ¹⁰ is bonded;
^The carbon atom to which ¹³ is bonded or the carbon atom to which R ¹¹ is bonded may be bonded directly or via an alkylene group having 1 to 3 carbon atoms, and when n = m = 0, R ¹⁵
And R ¹² or R ¹⁵ and R ¹⁹ may combine with each other to form a monocyclic or polycyclic aromatic ring. [A-2] A ring-opened polymer or copolymer of a cyclic olefin represented by the chemical formula [Chemical Formula 1] or [Chemical Formula 2], and [A-3] The ring-opened polymer or copolymer. Combined [A-2]
Hydride. 24. The DVD according to claim 16, wherein the composition contains a compound having a hydrophilic group and a hydrophobic group in the same molecule.
/ CD compatible optical pickup device. 25. In the objective lens, a focal length f
The DVD / CD compatible optical pickup device according to any one of claims 16 to 24, wherein 0.5 ≦ D / f ≦ 0.7 is satisfied between the optical pickup and the lens outer diameter D. 26. The method according to claim 16, wherein 0.4 mm ≦ Do−De ≦ 3.0 mm is established between the outer diameter Do of the objective lens and the effective diameter De. 2. A DVD / CD compatible optical pickup device according to item 1. 27. An end thickness of the objective lens is 0.9 mm.
The DVD / CD compatible optical pickup device according to any one of claims 16 to 26, wherein: 28. The method according to claim 16, wherein 0.45 ≦ t / f ≦ 0.73 is established between the axial thickness t of the objective lens and the focal length f. A DVD / CD compatible optical pickup device according to any of the above. 29. The DVD / CD compatible light according to claim 16, wherein the diffraction surface has a plurality of annular zones, and the total number of annular zones is 13 or more and 50 or less. Pickup device. 30. The objective lens according to claim 16, wherein the objective lens has an optical function part and a flange formed on an outer periphery thereof, and the flange has a notch. DVD / CD compatible optical pickup device. 31. The notch, when viewed in the optical axis direction,
31. The DVD according to claim 30, wherein a part of a substantially circular outer peripheral surface of the flange portion is a cut portion.
/ CD compatible optical pickup device. 32. The DVD / DVD according to claim 16, wherein a part of the image side surface of the objective lens has a surface extending in a direction substantially perpendicular to an optical axis.
CD compatible optical pickup device. 33. When the optical path difference function of the diffraction surface is φ (h) (h is a distance from the optical axis), dφ (h) / dh is discontinuous or substantially discontinuous at a predetermined distance h. The objective lens according to claim 1, wherein the objective lens is a continuous function. 34. A width in a direction perpendicular to the optical axis of an outermost annular zone of the annular zones formed inside the predetermined distance h is adjacent to the outermost annular zone and the predetermined distance h
34. The objective lens according to claim 33, wherein a width in a direction perpendicular to an optical axis of an annular zone formed outside the optical axis is smaller than the width. 35. When a CD is irradiated with light from a light source having a wavelength λ at a predetermined object distance, the wavefront aberration is 0.07λrms or less at a numerical aperture NA equal to or less than the predetermined distance h. 4. The spherical aberration of a ray passing inside h is smaller than the spherical aberration of a ray passing outside the predetermined distance h by 10λ to 100λ.
35. The objective lens according to 3 or 34. 36. The i-th diffractive annular zone of the diffractive surface, counting from the optical axis in a peripheral direction, satisfies the following expression. Objective lens. 1.2 ≦ p _{i + 1} / p _i ≦ 10 where p _i is the i-th diffraction ring zone counted from the optical axis in the peripheral direction,
Width in the direction perpendicular to the optical axis 37. The number m of a diffraction ring zone through which a light beam having an NA of 0.60 satisfies 22 ≦ m ≦ 32.
The objective lens according to any one of the above. However, the number of the diffraction ring zone is 1 on the ring zone on the optical axis, and it is counted outward in order. 38. The light beam has a wavelength of 630 to 665 nm.
38. The objective lens according to claim 37, wherein the light beam is incident as a substantially parallel light beam within the range. 39. The wavelength for DVD is λ1, the wavelength for CD is λ2 (λ1 <λ2), and the light flux of the wavelength λ1 determines the required numerical aperture on the image side required for recording or reproducing on DVD. NA1 and the required numerical aperture on the image side required for recording or reproducing a CD with the light beam of the wavelength λ2 is NA2 (NA1 ≧ NA2). For the combination, the wavefront aberration is 0.07λ1 rms or less, and for the combination of the wavelengths λ2 and CD and the required numerical aperture NA2, the wavefront aberration is 0.07λ2 rms or less, and the wavelength λ2 and CD The objective lens according to any one of claims 1 to 15, and 33 to 38, wherein the light flux having the required numerical aperture NA2 or more is flared for the combination of (i). 40. When the CD is irradiated with light from the light source of the wavelength λ2 located at a predetermined object distance, the light flux having the required numerical aperture NA2 or more and NA1 or less, has a diameter w2 or more and w1 or less on the recording surface of the CD. 40. The objective lens according to claim 39, wherein the objective lens satisfies 10 μm ≦ w2 ≦ 50 μm 20 μm ≦ w1−w2 ≦ 110 μm. 41. When a CD is irradiated with light from a light source having the wavelength λ2 at a predetermined object distance, the wavefront aberration is 0.07λ2rm at a numerical aperture NA equal to or less than the predetermined distance h.
s or less, and the spherical aberration of a light ray passing inside the predetermined distance h is smaller than the spherical aberration of a light ray passing outside the predetermined distance h by 10λ2 to 100λ2. 40. The objective lens according to 40. 42. The wavelength λ1 is 630 to 665 nm.
And the wavelength λ2 is 750 to 8
42. The objective lens according to claim 39, wherein the wavelength is in a range of 10 nm. 43. When the optical path difference function of the diffraction surface is φ (h) (h is a distance from the optical axis), dφ (h) / dh is discontinuous or substantially discontinuous at a predetermined distance h. The DVD / CD compatible optical pickup device according to any one of claims 16 to 32, wherein the optical pickup device is a continuous function. 44. A width in a direction perpendicular to the optical axis of an outermost annular zone of the annular zones formed inside the predetermined distance h is adjacent to the outermost annular zone and the predetermined distance h
44. A DVD / DVD according to claim 43, wherein the width of the annular zone formed outside the optical axis is smaller than the width in the direction perpendicular to the optical axis.
CD compatible optical pickup device. 45. When light is emitted from a light source having a wavelength λ at a predetermined object distance to a CD via the objective lens, the wavefront aberration is 0.07 λrms at a numerical aperture NA equal to or less than the predetermined distance h. The spherical aberration of a light beam passing inside the predetermined distance h is smaller than the spherical aberration of a light beam passing outside the predetermined distance h by 10λ to 100λ.
45. A DVD / CD compatible optical pickup device according to 3 or 44. 46. The i-th diffractive annular zone of the diffractive surface counted from the optical axis in the peripheral direction satisfies the following expression. DVD / CD compatible optical pickup device. 1.2 ≦ p _{i + 1} / p _i ≦ 10 where p _i is the i-th diffraction ring zone counted from the optical axis in the peripheral direction,
Width in the direction perpendicular to the optical axis 47. The number m of the diffraction ring zone of the diffraction surface through which a light ray of NA 0.60 passes, satisfying 22 ≦ m ≦ 32.
7. A DVD / CD compatible optical pickup device according to any one of 6. 48. Among the two light sources, the wavelength of the light source for DVD is λ1, and the wavelength of the light source for CD is λ2 (λ1 <λ).
The required numerical aperture on the image side required for performing recording or reproduction of a DVD with the light beam of the wavelength λ1 is set to NA1, and the recording or reproduction of a CD is performed with the light beam of the wavelength λ2. When the required numerical aperture on the image side is NA2 (NA1 ≧ NA2), the wavefront aberration is 0.07λ1 rms or less with respect to the combination of the wavelength λ1 and the DVD and the required numerical aperture NA1. Wavefront aberration is 0.07λ2 rms or less for a combination of CD and the required numerical aperture NA2, and a light beam having the required numerical aperture NA2 or more for the combination of the wavelength λ2 and CD is flared. The DVD / CD compatible optical pickup device according to any one of claims 16 to 32 and 43 to 47. 49. When light is irradiated from a light source having the wavelength λ2 at a predetermined object distance to the CD via the objective lens, the light flux having the required numerical aperture NA2 or more and NA1 or less is recorded on the recording surface of the CD. 49. The DVD / DVD according to claim 48, wherein the distribution is in the range of w2 or more and w1 or less, and satisfies 10 μm ≦ w2 ≦ 50 μm 20 μm ≦ w1-w2 ≦ 110 μm.
CD compatible optical pickup device. 50. The object point of the objective lens for the combination of the wavelength λ1 and the DVD and the object point of the objective lens for the combination of the wavelength λ2 and the CD are at an optically equal distance. Claim 48 or 4
10. A DVD / CD compatible optical pickup device according to item 9. 51. The wavelength λ1 is 630 to 665 nm
And the wavelength λ2 is 750 to 8
The DVD / CD compatible optical pickup device according to any one of claims 48 to 50, wherein the wavelength is in a range of 10 nm. 52. The amount of spherical aberration when a light beam having a wavelength λ having a numerical aperture NA of 0.5 to 0.7 passes when the light beam having a wavelength λ having a numerical aperture NA less than 0.5 passes. 35. The objective lens according to claim 33, wherein the amount of spherical aberration is larger than the amount of spherical aberration by 10? 53. The objective lens, wherein a numerical aperture NA is equal to 0.
The spherical aberration amount when the light beam of the wavelength λ2 in the range of 5 to 0.7 passes is smaller than the spherical aberration amount when the light beam of the predetermined wavelength λ2 passes when the required numerical aperture NA is less than 0.5. 52. The DVD according to any one of claims 48 to 51, wherein the size of the DVD is 10λ2 to 100λ2 or more.
/ CD compatible optical pickup device. 54. The objective lens having a numerical aperture NA of 0.1.
When a light flux of less than 5 passes, the light flux reflected from the CD is irradiated toward the light receiving means so as to be included in the light receiving surface of the light receiving means, and the light flux having a numerical aperture NA of 0.5 or more is emitted. When you pass, CD
43. A light beam reflected from the light source irradiates the surroundings of the light receiving unit except for the light receiving surface.
54. A DVD / CD compatible optical pickup device according to any one of items 51 to 53. 55. The light-receiving means has one to three substantially rectangular light-receiving surfaces, and the numerical aperture NA is equal to 0.
Spot diameter of 5 or more luminous flux on CD recording surface is 5 μm
55. The DVD according to claim 54, wherein:
/ CD compatible optical pickup device. 56. The light receiving means has three rectangular light receiving surfaces arranged substantially on a straight line, and the numerical aperture NA is 0.5.
The spot diameter of the above light beam on the recording surface of the CD is 25 μm.
55. The DVD according to claim 54, wherein:
/ CD compatible optical pickup device. 57. When a light beam having a required numerical aperture NA of 0.5 or more passes through the objective lens, the light beam reflected from the CD is directed toward the light receiving means so as to include only the peripheral light receiving surface. Irradiation is performed.
DVD / C according to any of 32, 43 to 51, 52
D compatible optical pickup device. 58. The light-receiving means has at least two stripe-shaped light-receiving surfaces, and a spot diameter of a light flux having a numerical aperture NA of 0.5 or more on a recording surface of a CD is 20 μm or more. The DVD / DVD according to claim 57, characterized in that:
CD compatible optical pickup device. 59. The light receiving means has at least four stripe-shaped light receiving surfaces, and a spot diameter of a light beam on a recording surface of a CD having a numerical aperture NA of 0.5 or more is 50 μm or more. The DVD / DVD according to claim 57, characterized in that:
CD compatible optical pickup device.